Processing of viscose rayon



Patented June 20, 1933 was ATES

GEORGE A. RICHTER AND PHILIP G. SCHERER, JR., OF BERLIN, NEW HAMPSHIRE,

ASSIGNORS TO BROWN COMPANY, OF BERLIN, NEW HAMPSHIRE, A CORPORATION OFMAINE No Drawing.

This invention relates to the processing of viscose-rayon, and dealsmore particularly with the treating operations to which crudeviscose-rayon yarn (i. e.,,yarn coming from 5 the spinning bath) issubjected before being used as a raw material in the manufacture ofrayon goods. I

Crude rayon yarn contains considerable sulphur and an appreciable amountof organic coloring matter, even after it has been Washed and dried. Inorder to produce yarn of the desired luster and whiteness, it has beenfound necessaryto subject the crudeyarn to desulphuriz'ing anddecolorizing treatments. Desulphurization isusually accomplished bytreating the yarn with dilute solutions of sodium sulphide at about 80to 100 C., whereupon after washing and souring to remove traces ofsodium sulphide, the desulphurized yarn isdecolorized by bleaching aswith dilute chlorine water. The decolorized yarn is then washed, treatedwith antichlor solution, e. g., sulphurous acid, N again washed, andfinally dried. This sequence of treating operations heretofore commonlypractised in the industry involves considerable handling of wet rayonyarn, and accordingly is time-consuming and expenslve.

We have discovered that it is possible to desulphurize and decolorizecrude viscoserayon yarn to the desired condition, if such yarn isimmersed in an alkaline bath and oxygen in suitable form is supplied tothe bath. Thus, -we have found that the yarn may be desulphurized anddecolorized in a single step, if it is immersed in a hot, dilutealkaline solution and a current of oxygencontaining gas, e. g., air oroxygen, passed into the solution. We have further'found that similarresults may be obtained by dis- PROCESSING OF VISGOSE RAYON Applicationfiled December 2'7, 1928. Serial No. 328,852.

resulting from the processes heretofore employed. The process of thepresent inven tion thus makes possible the removal of sulphur andcoloring mater from crude ViSCOSB-r rayon yarn by a simpler, lessexpensive process, comprising fewer steps, consuming much less time, andyielding a product of excellent characteristics.

While we do not know precisely the action r of the ferric or manganesesalts on the yarn, in view of the fact that organic coloring mat ter isremoved therefrom, it is highly probable that these salts slowly furnishnascent oxygen, which exerts a bleaching effect. The

.E'zvample 1 Crude rayon yarn, say in skein form or wound on a reel, isimmersed in a hot, dilute solution of sodium hydroxide, preferably a0.2% solution, at to 100 C. -A current ofair or oxygen is passed intothe solution until the yarn is thoroughly desulphurized; (about 30minutes), at which time it is also bleached to snow-whiteness. The yarnis then removed from the solution, thoroughly washed with water,anddried.

Example 2 v Crude rayon yarn is immersed in a hot, dilute solution ofsodium hydroxide containing ferric or manganese salts, preferably in a0.2% solution containing about 0.2% ferric nitrate or manganese sulphateand at 80 to 100 C. The solution. is maintained at this temperature andis stirred until desulphurization is complete (about 30 minutes)whereupon the yarn is removed from the bath. The colored ferric ormanganese salts deposited subsequently washed and dried, a pure whiteproduct is obtained.

E wample 5 Crude rayon yarn is immersed in a hot, dilute solution ofsodium hydroxide contammg ferric or manganese salts, preferably 1n a 12%solution containing about 0.2% ferric nitrate-or manganese sulphate-andat 80 to 100C. Into the solution is passed a current of air or oxygen,until desulphurization is complete (about 30 minutes). The yarn is .thenremoved from the solution, treated as described in Example 2 for theremoval of the colored iron or manganesesaltsdeposited thereon, and thenwashed and dried.

The foregoing examples are merely illustrative, as there are variousother alkaline compounds and catalytic oxidizing agents which may beused in the treating bath. ,F or instance, in lieu-of caustic soda, wemay use such alkaline salts as sodium carbonate, sodium phosphate,borax, or the like, andin lieu of ferric or manganese salts, we mayuseothersalts, such as those of cobalt, nickel, chromium, and vanadium,which in the presence of organic reducing agents tendeto change valencefrom higher to lower form, the concentration .of solution and the temperature and time of treatment being such as will best suit the yarnbeing treated.

Having thus described the process of the present invention and certainmodes of practising the same, it should be evident to those skilledinthe art that various changes and modifications might be made thereinwithout departing from the spirit orscope of invention as defined by theappended claims.

We claim:

1. A process which comprises treating crude viscose-rayon yarn with analkaline solution whileprogressively furnishing the solution with oxygenfrom an outside source until the yarn has been desulphurized.

2. A process which comprises maintaining crude viscose-rayon yarn incontact with an alkaline solution while progressively .furnishing thesolution with oxygen from an outside source until the yarn has beendesulphurized, and washing the product.

3. A process which comprises maintaining crude viscose-rayon yarn incontact with a hot, dilute alkaline solution while progressivelyfurnishingthe solution with oxygen from an outside source until the yarnhas been desulphurized.

4-. A process which comprises immersing crude viscose-rayon yarn in analkaline solution containing a catalytic oxidizing agent, and passing anoxygen-containing gas into the solution.

5. A process which comprises immersing crude viscose-rayon yarn in analkaline solution, and passing an oxygen-containing gas into thesolution.

v6. A process which comprises maintaining crude viscose-rayon yarn incontact with an alkaline solution containing a catalytic oxidizing agentuntil the yarn has been desulphurized, said agent being selected from agroup consisting of iron, manganese, cobalt,

nickel, chromium, and vanadium salts.

7. A process which comprises maintaining crude viscose-rayon yarn incontact with an alkaline solution containing a colored catalyticoxidizing agent selected from agroup consistingof iron, manganese,cobalt, nickel, chromium and vanadium salts, until .the yarn has beendesulphurized, and removing the colored agentdeposited on the yarn.

8. A process which comprises maintaining crude viscose-.rayon yarnincontact with an alkaline solution containing a ferric salt until theyarn has been desulphurized,.and removing the salt deposited on theyarn.

, 9. A process which comprises maintaining crude viscose-rayon yarnincontact with an alkaline solution containing a ,ferr1c salt until theyarn has been desulphurized, treating with oxalicacid solution to removethe salt deposited on the yarn, and washing.

10. A process which comprises maintaining crude viscose-rayon yarn incontact with an alkaline solution containing ferric nitrate untiltheyarn has been desulphurized,,treating with oxalic acid solution toremove the salt deposited on the yarn, and washing.

.11. A process which comprises maintaining crude viscose-rayon yarn incontact with an alkaline solution containing a manganese salt unitltheyarn has been desulphurized, and removing the salt deposited on theyarn.

12. A process which comprises maintaining crude viscose-rayon yarn incontact with an alkaline solution containing a manganese salt until theyarn has been desulphurized, treating with sulphurous acid solution toremove the salt deposited on the yarn, and washing. 13. A process whichcomprises maintaining crude viscose-rayonyarn in contact with analkaline solution containing manganese sulphate until the yarnhas beendesulphur 'ized, treating with sulphurous acid solution an alkalinesolution containing the compound of an element having more than onevalence and tending to change from higher GEORGE A. RICHTER. PHILIP C.SCHERER, JR.

